Armina californica feeding, eye spots

May 29, 2006
From: Mike Neubig

Armina californica happens to be one of my favorite nudibranchs, so it was a pleasure to find several this morning in conditions of bright sunshine and low-surge. Both photos are of the same individual, however, and in the first, I'm guessing the Armina is about to dine.

Both photos reveal a prominent black spot on the side of the head tentacle (or are they rhinophores?), which I'm guessing are eye spots. These were bilateral, and can be seen in one of Paul Sim's photos [message #14043]. It's more common for me to dive at night, and the eye spots, if that is what they are, might explain why Armina tend to dive into the sand when I position my camera rig (dual HIDs) for macro shots, and why I had much better luck in today's bright waters.

Locality: Valley-Sea-Toes, La Jolla Shores, 13m, California, USA, Eastern Pacific Ocean, 19 May 2006, sandy sloping shoulder of La Jolla Canyon. Length: 30mm. Photographer: Mike Neubig.

Mike Neubig

mike.neubig@gmail.com

Neubig, M., 2006 (May 29) Armina californica feeding, eye spots. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16674

Dear Mike,
Yes the tentacles are their rhinophores. On the rhinophore Fact Sheet you will see that the arminid group are the only nudibranchs which have vertical rather than horizontal leaflets on the rhinophores.

The black spot is indeed the eye, but as they can't form images the only way you would disturb is if you cast a shadow over it [unlikely at night]. I am sure someone will be able to tell us about the daily rhythm of Armina californica. I am not sure if they are usually nocturnal, like many nudibranchs, to avoid fish predators, or whether they follow the cycle of emergence of the sea pens they feed on. I assumed that both the sea pens and Armina only emerged at night but as Jan Kocian's messages [see #14935] showed, Armina will emerge for a  feed during the day if the sea pens have been ripped out of the substrate. It would be interesting to know what the food of Armina is in your area and if is sea pens, are they normally out during the day?
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (May 29). Comment on Armina californica feeding, eye spots by Mike Neubig. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16674

Factsheet

Armina californica

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